Receiving billing and shipping details during checkout and sending the final quote and payment terms (Node.js)

In this use case, the user confirms a slot by providing additional details of the patient like medical history, prescription etc and receives final invoice along with payment terms

Code snippets

BPP receives protocol init

/*
Example Request JSON:
{
    "context": {
        "domain": "nic2004:85121",
        "country": "IND",
        "city": "std:080",
        "action": "init",
        "core_version": "0.9.2",
        "bap_id": "https://mock_bap.com/",
        "bap_uri": "https://mock_bap.com/beckn/",
        "transaction_id": "1239890342",
        "message_id": "123793824",
        "timestamp": "2021-03-23T10:00:40.065Z"
    },
    "message": {
        "order": {
            "items": [
                {
                    "id": "dr_veena_slot_1",
                    "quantity": {
                        "count": 1
                    }
                }
            ],
            "billing": {
                "name": "John Doe",
                "address": {
                    "door": "21A",
                    "name": "ABC Apartments",
                    "locality": "HSR Layout",
                    "city": "Bengaluru",
                    "state": "Karnataka",
                    "country": "India",
                    "area_code": "560102"
                },
                "email": "[email protected]",
                "phone": "+919876543210"
            },
            "fulfillment": {
                "type": "IN-PERSON",
                "end": {
                    "location": {
                        "id": "good-health-koramangala",
                        "gps": "12.9349377,77.6055586"
                    },
                    "time": {
                        "range": {
                            "start": "2021-08-11T04:30:00.000Z",
                            "end": "2021-08-11T05:30:00.000Z"
                        }
                    },
                    "contact": {
                        "phone": "+919876543210",
                        "email": "[email protected]"
                    }
                }
            }
        }
    }
}
*/
    // Auth middleware authenticates the digital signature of the incoming request
    router.post('/healthcare_consultation/init', auth, init);

    function init({ headers, body }, res) {
        try {
            const message = _.get(body, "message");
            const context = _.get(body, "context");
            if (!context) {
                return res.status(400).send(httpResponse("NACK", "Missing Context"));
            }
            if (!message) {
                return res.status(400).send(httpResponse("NACK", "Missing Message"));
            }
            // ... Returns the ack immediately and continue the processing after validation
            res.status(200).send(httpResponse("ACK"));
            function processInit(headers, body)
        } catch (error) {
            res.status(500).send(httpResponse("NACK", error));
        }
    };

BPP processes the init

    function processInit(requestHeaders, initRequestBody) {
        // Execute business logic here
        let initResponse = {}
        generateResponse(requestHeaders, initResponse)
    }

BPP generates response

    async function generateResponse(requestHeaders, rawResponse){
/*
Example Request JSON :
{
    "context": {
        "domain": "nic2004:85121",
        "country": "IND",
        "city": "std:080",
        "action": "on_init",
        "core_version": "0.9.2",
        "bap_id": "https://mock_bap.com/",
        "bap_uri": "https://mock_bap.com/beckn/",
        "transaction_id": "1239890342",
        "message_id": "123793824",
        "timestamp": "2021-03-23T10:00:40.065Z"
    },
    "message": {
        "order": {
            "items": [
                {
                    "id": "dr_veena_slot_1",
                    "quantity": {
                        "count": 1
                    }
                }
            ],
            "billing": {
                "name": "John Doe",
                "address": {
                    "door": "21A",
                    "name": "ABC Apartments",
                    "locality": "HSR Layout",
                    "city": "Bengaluru",
                    "state": "Karnataka",
                    "country": "India",
                    "area_code": "560102"
                },
                "email": "[email protected]",
                "phone": "+919876543210"
            },
            "fulfillment": {
                "type": "IN-PERSON",
                "end": {
                    "location": {
                        "id": "good-health-koramangala",
                        "gps": "12.9349377,77.6055586"
                    },
                    "time": {
                        "range": {
                            "start": "2021-08-11T04:30:00.000Z",
                            "end": "2021-08-11T05:30:00.000Z"
                        }
                    },
                    "contact": {
                        "phone": "+919876543210",
                        "email": "[email protected]"
                    }
                },
                "agent": {
                    "name": "Dr. Veena H",
                    "dob": "1989-08-12",
                    "gender": "Female",
                    "tags": {
                        "doctor_registration_no": "12345"
                    },
                    "phone": "+919876543210",
                    "email": "[email protected]"
                }
            },
            "quote": {
                "price": {
                    "currency": "INR",
                    "value": "1100"
                },
                "breakup": [
                    {
                        "title": "Consultation Charges",
                        "price": {
                            "currency": "INR",
                            "value": "1000"
                        }
                    },
                    {
                        "title": "Service Charge",
                        "price": {
                            "currency": "INR",
                            "value": "100"
                        }
                    }
                ],
                "ttl": "P1H"
            },
            "payment": {
                "uri": "https://api.bpp.com/pay?amt=$amount&txn_id=ksh87yriuro34iyr3p4&mode=upi&vpa=bpp@upi",
                "tl_method": "http/get",
                "params": {
                    "transaction_id": "ksh87yriuro34iyr3p4",
                    "amount": "1100",
                    "mode": "upi",
                    "vpa": "bpp@upi"
                },
                "type": "ON-FULFILLMENT",
                "status": "NOT-PAID"
            }
        }
    }
}
*/
        let onInitResponseBody = {

        }
        //call protocol on_init
        await callOnInit(requestHeaders, onInitResponseBody);
    }

BPP calls protocol on_init

    async function callOnInit(requestHeaders, onInitResponseBody) {
        // Take the subscriber Id from the header and calls the registry to get the url. If already cached it need not to call again
        const uri = await lookup(requestHeaders);
        // Construct Header
        const headers = constructAuthHeader(); // Auth Header with digital Signature
        return axios({ url: `${uri}/healthcare_consultation/on_init`, method: "POST", headers, data: onInitResponseBody });
    }